Because of curl and core-set specifications, an advanced photo system (APS) film uses a polyethylene naphthalate based support that must be annealed before applying the emulsion layers. The film support can be prepared by purchasing oriented PEN base, annealing the base, and then applying the adhesive (subbing) and backing layers forming the following structure:
Gel based sub adhesion layer PEN support adhesive layer antistat/binder magnetics layer lubricant
To reduce manufacturing costs it would be desirable to manufacture the PEN support and apply as many of the support coatings in-line with the base manufacturing before annealing in a wound roll format. The current magnetics coated support undergoes degradation with annealing resulting in poor magnetics layer adhesion. One method of improving adhesion is the addition of crosslinking agents to the magnetics layer, such as isocyanates, a known skin and respiratory sensitizor. Because of health and safety concerns with handling isocyanates it is desirable to use an alternative crosslinking agent. We have found that good adhesion can be achieved by the use of heat activated blocked isocyanates in the magnetics layer. These materials will crosslink the coating during the annealing stage of manufacturing (application of heat over a long period of time). The added advantage of these materials is that they do not react at room temperature and thereby extend the life of a coating solution and provide easy clean-up.
U.S. Pat. No. 4,225,665 describes an antistat layer that contains a carboxylic acid functionalized polymer which is crosslinked with aziridine.
U.S. Pat. No. 5,198,499 describes an antistat layer that is crosslinked with a melamine which provides good abrasion resistance, adhesion and antistatic properties.
U.S. Pat. No. 5,427,900 decries a photographic film with a magnetics layer on the backside. The preferred binder for the magnetics layer is cellulose diacetate which may be crosslinked with isocyanates, aziridines or melamines.
U.S. Pat. No. 5,432,050 describes a magnetics layer with filler particles which may be crosslinked with isocyanates, aziridines or melamines.
If the magnetics package is applied before the annealing process, the adhesion of the backings is degraded because of the annealing process. It would be advantageous to coat as many backside layers as possible in-line before annealing.